Lab-Scale Investigation of Fenton and Photo-Fenton Processes for Removal of Pollutants from Textile and Dye-Intermediate Industrial Wastewater, Ahmedabad Industrial Estate, Gujarat, India
Description
This study investigates the physico-chemical characteristics and treatment efficacy of effluents from the Ahmedabad Industrial Estate, Gujarat, India, employing two Advanced Oxidation Processes: Fenton and Photo-Fenton. The study focused on a comprehensive suite of parameters, including pH, colour, turbidity, Total Suspended Solids, Total Solids, Total Dissolved Solids, Chemical Oxygen Demand, Biochemical Oxygen Demand, Chloride, Ammoniacal Nitrogen, Nitrate, Sulphate, and Phosphate. Experiments were conducted on 1-litre effluent samples at three volumetric ratios of ferrous ion to hydrogen peroxide: 1:10, 1:20, and 1:30. The Photo-Fenton process followed an identical protocol, with the addition of continuous UV light exposure to accelerate reaction kinetics. The results consistently demonstrated that pollutant removal efficiency correlated positively with the reactant ratio, with the 1:30 ratio yielding the highest performance across all parameters. Colour removal reached 74.11%, turbidity 83.62%, and TSS 72.49%. COD reduction was more modest, ranging between 9.09% and 31.97%. This stream showed significant susceptibility to Fenton oxidation. COD removal was remarkably high (up to 97.89%), while turbidity and TSS removal reached 98.50% and 92.60%, respectively. The inclusion of UV radiation enhanced the breakdown of pollutants, particularly in complex dye-intermediate matrices. TDS removal was notably improved, reaching 75.39%. Colour removal spanned 28.88% to 71.25%, with TSS reduction hitting 92.72%. This process proved highly efficient for organic degradation, achieving up to 96.61% COD removal. TSS removal peaked at 94.37%, confirming the process's viability for solid-liquid separation and organic mineralization. A recurring trend across both treatments was a negative removal value for sulphate. This is attributed to the addition of ferrous sulphate as a catalyst, which naturally increases the residual sulphate concentration in the effluent. While this is a by-product of the chemical dosing, it is a critical factor for post-treatment management. The study confirms that dye-intermediate effluents are generally more responsive to these oxidative treatments than textile effluents. The transition from the 1:10 to the 1:30 ratio consistently improved performance, suggesting that optimizing the peroxide dosage is paramount for maximum pollutant mineralization. Both Fenton and Photo-Fenton oxidation processes are highly effective, sustainable solutions for the pre-treatment of industrial wastewater in the Ahmedabad region. By leveraging the high oxidative potential of the hydroxyl radical, these methods offer a robust pathway for reducing the environmental footprint of textile and dye-intermediate manufacturing. Given the high removal efficiencies observed—particularly at the 1:30 ratio—these AOPs represent a viable, eco-friendly strategy to meet stringent discharge standards and promote water circularity in industrial zones.
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Steps to reproduce
1. Preparation of Fenton’s Reagent Reagent Synthesis: Dissolve 69.50 g of analytical-grade ferrous sulphate (FeSO4.7H2O) into 500 mL of sterilized deionized (DI) water. Acidification: Carefully add 5 mL of concentrated sulfuric acid (H2SO4) to the solution. This creates an acidic environment essential for stabilizing the ferrous ions and optimizing the subsequent catalytic reaction. Ensure the solution is stored in an airtight container to prevent premature oxidation of iron. 2. Experimental Setup and Effluent Preparation Sample Collection: Collect 1-litre samples of industrial effluent from the designated source. Ensure samples are representative of the raw waste stream. pH Optimization: Measure the initial pH of the raw effluent. Adjust the sample to an acidic range (pH 2.0–3.0) using dilute H2SO4. This pH range is critical for the generation of hydroxyl radicals (.OH) via the Fenton reaction. 3. Execution of the Fenton Process Dosing: For each 1-litre sample, prepare the three experimental ratios of ferrous catalyst to hydrogen peroxide (H2O2): 1:10 Ratio: 1 mL catalyst solution to 10 mL H2O2. 1:20 Ratio: 1 mL catalyst solution to 20 mL H2O2. 1:30 Ratio: 1 mL catalyst solution to 30 mL H2O2. Reaction Phase: Introduce the Fenton reagent into the 1-litre effluent sample under continuous agitation using a magnetic stirrer. Maintain constant speed for exactly one hour to ensure uniform distribution of the catalyst and oxidant. Settling: After the one-hour reaction period, stop the stirring. Allow the mixture to settle under quiescent conditions. This allows the suspended solids and flocs formed during the oxidation process to precipitate out of the solution. Collection: Carefully extract the supernatant (the clarified liquid at the top) for laboratory analysis of the target parameters (e.g., COD, TDS, colour, turbidity). 4. Execution of the Photo-Fenton Process The Photo-Fenton process follows the exact same dosing and settling protocol as the Fenton process with one critical addition: UV Exposure: During the one-hour reaction phase, the reactor vessel must be placed inside a UV-shielded cabinet equipped with a UV light source. The sample must be continuously stirred while being exposed to the radiation. The UV light facilitates the photoreduction of ferric ions back into ferrous ions, thereby accelerating the cycle of hydroxyl radical production. 5. Data Analysis and Validation Standard Methods: Analyze the supernatant using standard wastewater examination methods for all physicochemical parameters. Control Baseline: Always analyze an untreated sample alongside the treated samples to calculate precise removal efficiency percentages. Sulphate Correction: Note that the addition of ferrous sulphate will inherently increase sulphate levels. When reporting data, differentiate between the sulphate reduction capacity of the treatment and the residual sulphate introduced by the catalyst itself.
Institutions
- The Charutar Vidya Mandal (CVM) UniversityGujarat, Vallabh Vidyanagar